Neoclassical economics is grouping of a number of schools of thought in economics. There is not complete agreement on what is meant by neoclassical economics -- in particular, vision, problem domains, and particular concerns vary among neoclassical economists.

Given, a certain population, with certain needs and powers of production, in possession of certain lands and other sources of material: required, the mode of employing their labour which will maximize the utility of their produce.

Neoclassical economics emphasizes equilibria, where equilibria are the solutions of individual maximization problems. Regularities in economies are explaned by methodological individualism, the doctrine that all economic phenonema can be ultimately explained by aggregating over the behavior of individuals. The emphasis is on microeconomics. Institutions, which might be considered as prior to and conditioning individual behavior, are de-emphasized. Economic subjectivism accompanies these emphases. See also general equilibrium.

Neoclassical economics is conventionally dated from William Stanley Jevons' Theory of Political Economy (1871), Carl Menger's Principles of Economics (1871), and Leon Walras's Elements of Pure Economics (1874-1877). These three economists have been said to have promulgated the marginal utility revolution, or Neoclassical Revolution. Historians of economics and economists have debated

Whether utility or marginalism was more essential to this revolution (whether the noun or the adjective in the phrase "marginal utility" is more important)

Whether there was a revolutionary change of thought or merely a gradual development and change of emphasis from their predecessors

Whether grouping these economists together disguises differences more important than their similarities.

In particular, Walras was more interested in the interaction of markets than in explaining the individual pysche through a hedonistic psychology. Jevons saw his economics as an application and development of Jeremy Bentham's utilitarianism and never had a fully developed general equilibrium theory. Menger emphasized disequilibrium and the discrete. Menger had a philosophical objection to the use of mathematics in economics, while the other two modeled their theories after 19th century mechanics.

Alfred Marshall's textbook, Principles of Economics (1890), was the dominant textbook in England a generation later. Marshall's influence extended elsewhere; Italians would compliment Maffeo Pantaleoni[?] by calling him the "Marshall of Italy". Marshall thought classical economics attempted to explain prices by the cost of production[?]. He asserted that the neoclassicals went too far in correcting this imbalance by overemphasizing utility and demand. Marshall thought the question of whether supply or demand was more important was analogous to the pointless question of which blade of a scissors did the cutting.

Marshall explained prices by the intersection of supply and demand curves. The introduction of different market "periods" was an important innovation in Marshall:

Market period. The goods produced for sale on the market are taken as given data, e.g. in a fish market. Prices quickly adjust to clear markets.

Short period. Industrial capacity is taken as given. The level of output, the level of employment, the inputs of raw materials, and prices fluctuate to equate marginal cost[?] and marginal revenue[?], where profits are maximized. Economic rents exist in short period equilibrium for fixed factors, and the rate of profit is not equated across sectors.

Long period. The stock of capital goods, such as factories and machines, is not taken as given. Profit-maximizing equilibria determine both industrial capacity and the level at which it is operated.

Very long period. Technology, population trends, habits and customs are not taken as given, but allowed to vary in very long period models.

Marshall took supply and demand as stable functions and extended supply and demand explanations of prices to all runs. He argued supply was easier to vary in longer runs, and thus became a more important determinate of price in the very long run.

An important change in neoclassical economics occurred around 1933. Joan Robinson[?] and Edward H. Chamberlin, with the near simultaneous publication of their respective books, The Economics of Imperfect Competition (1933) and The Theory of Monopolistic Competition (1933), introduced models of imperfect competition. Theories of market forms and Industrial Organization[?] grew out of this work. They also emphasized certain tools, such as the marginal revenue[?] curve.

These developments were accompanied by the introduction of new tools, such as indifference curves and the theory of ordinal utility. The level of mathematical sophistication of neoclassical economics increased. Paul Samuelson's Foundations of Economic Analysis (1947) contributed to this increase in formal rigor.

The interwar period in American economics has been argued to have been pluralistic, with neoclassical economics and institutialism[?] competing for allegiance. Frank Knight[?], an early Chicago school economist attempted to combine both schools. But this increase in mathematics was accompanied by greater dominance of neoclassical economics in Anglo-American universities after World War II.

Hicks' book had two main parts. The second, which was arguably not immediately influential, presented a model of temporary equilibrium. Hicks was influenced directly by Hayek's notion of intertemporal coordination and paralleled by earlier work by Lindhal. This was part of an abandonment of disaggregated long run models. This trend probably reached its culmination with the Arrow-Debreu model[?] of intertemporal equilibrium. The Arrow-Debreu model has canonical presentations in Gerard Debreu's Theory of Value (1959) and in Arrow and Hahn.

Neoclassical economics is frequently criticised for having a normative bias. In this view, it does not focus on explaining actual economies, but instead on describing a "utopia" in which Pareto optimality obtains. Key assumptions of neo-classical economics which are widely criticised as unrealistic include:

The focus on individuals in the economy may obscure analysis of wider long term issues, such as whether the economic system is desirable and stable on a finite planet of limited natural capital.

The assumption that individuals act rationally may be viewed as ignoring important aspects of human behavior. Mnay see "economic man" as being demonstrably different to a real man on the real earth. Large corporations might perhaps come closer to the neoclassical ideal of profit maximisation, but this is not necessarily viewed as desirable if this comes at the expense of a "locust-like" neglect of wider social issues. But they are not human, and are increasingly criticized for not being human. The assumption of rational expectations which has been introduced in more modern neo-classical models (sometimes also called new classical) may also be strongly criticised on the grounds of realism.

Problems with making the neoclassical general equilibrium theory compatible with an economy that develops over time and includes capital goods. This was explored in a major debate in the 1960s - the Cambridge Capital Controversy[?] - about the validity of neoclassical economics, with an emphasis on the theory of growth[?], capital, aggregate theory, and the marginal productivity theory[?] of distribution. There were also internal attempts by neoclassical economists to extend the Arrow-Debreu model to disequilibrium investigations of stability and uniqueness. Some think the Sonnenschein-Mantel-Debreu results put paid to these attempts.

In the opinion of some, these developments have found fatal weaknesses in neoclassical economics. Economists, however, have continued to use highly mathematical models, and many equate neoclassical economics with economics, unqualified. Mathematical models include those in game theory, linear programming, and econometrics, many of which might be considered non-neoclassical. So economists often refer to what has evolved out of neoclassical economics as "mainstream economics".

The critique of the assumption of rationality is not confined to social theorist and ecologists. Many economists, even contemporaries, have criticized this vision of economic man. Thorstein Veblen put it most sardonically:

lightning calculator of pleasures and pains, who oscillates like a homogeneous globule of desire of happiness under the impulse of stimuli that shift about the area, but leave him intact.

Herbert Simon's theory of bounded rationality has probably been more influential. Is economic man a first approximation to a more realistic psychology, an approach only valid in some sphere of human lives, or a general methodological principle for economics? Early neoclassical economists often leaned toward the first two appoaches, but the latter has become prevalent.

Neoclassical economics is also often seen as relying too heavily on complex mathematical models, such as those used in general equilibrium theory, without enough regard to whether these actually describe the real economy. Many see an attempt to model a system as complex as a modern economy by a mathematical model as unrealistic and doomed to failure.

Critics of neoclassical models accuse it of copying of 19th century mechanics and the "clockwork" model of society which seems to justify elite privileges as arising "naturally" from the social order based on economic competititions. This is echoed by modern critics in the anti-globalization movement who often blame the neoclassical theory, as it has been applied by the IMF in particular, for inequities in global debt and trade relations. They assert it ignores the complexity of nature and of human creativity, and seeks mechanical ideas like equilibrium:

And in Poinset's Elements de Statique..., which was a textbook on the theory of mechanics bristling with systems of simultaneous equations to represent, among other things, the mechanical equilibrium of the solar system, Walras found a pattern for representing the catallactic equilibrium of the market system. (William Jaffe)